The idea of using strace was a good one. I did that too, and the last thing
ktorrent tried to access was /proc/sys/crypto/fips_enabled
google shows this is used by libgcrypt and indeed my libgcrypt was not
updated.
So I updated it to 1.5.0-3, and it fixed the problem, ktorrent can now
start normally again !
Thanks for the idea, it was half of the job ! ;-)